Purpose :
The pathophysiological mechanism of Leber’s Hereditary Optic Neuropathy (LHON), which is caused by mutations in mitochondrial complex I, is not well understood. Using the Ndufs4 knockout (KO) as a mouse model of LHON, we established previously that mitochondrial complex I deficiency leads to an innate immune and inflammatory wave that coincides with vision loss in these mice as well as death of starburst amacrine cells and retinal ganglion cells. We hypothesize that intervention with drugs that either inhibit the inflammatory response or increase ATP synthesis will preserve visual function and prevent neurodegeneration.

Methods :
Ndufs4 knockout mice and littermate controls were treated with vehicle or one of four drugs, multiple of which were protective in a high-throughput screen of LHON cells, to be identified later due to disclosure restrictions; R (8 mg/kg), Z (20 mg/kg), D (10 mg/kg), or P (20 mg/kg). Doses were administered intraperitoneally daily for 14 days. Visual cliff testing was performed prior to dosing at P21 and at the end of treatment at P35. Mice were then sacrificed and retinas collected for qRT-PCR and flat mount immunostaining for ChAT expression.

Results :
All four drugs preserved visual function in the Ndufs4 KO compared with Ndufs4 KO dosed with vehicle, which were unable to detect the edge in the visual cliff test. Drugs R and P significantly inhibited innate immune and inflammatory transcripts that were elevated in the Ndufs4 KO, such as B2m, Cxcl10, Ccl5, Ccl12, Aif1, Tlr2, and Tlr4, demonstrated by qRT-PCR. Drug R was able to prevent neurodegeneration of starburst amacrine cells, which was performed by counting ChAT-positive cells using confocal microscopy.

Conclusions :
An innate immune and inflammatory response and starburst amacrine cell death appear to be early consequences of complex I deficiency in the Ndufs4 KO mouse model of LHON, and may be relevant to the pathomechanism of human LHON. Drug screening has identified four drugs that rescue mitochondrial blindness in the Ndufs4 context. R, Z, D, and P were shown to preserve visual function in Ndufs4 KO mice, and could be considered as therapeutic leads for LHON. The differential suppression of inflammatory molecules of the different drugs suggests differential mechanisms of protection.

This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.